2 MISER AND FAIRCHILD: HAUSMANNITE 



site, and wad have been identified. They generally occur in 

 rough irregular-shaped masses from less than one pound to 22 

 tons in weight. Most of the masses are in clay; the others are 

 in limestone, shale, chert, and sandstone, and there is much evi- 

 dence that the manganese oxides of which the masses are com- 

 posed have replaced all of these inclosing materials. The oxides 

 have been derived from manganese-bearing carbonates near the 

 surface and have been deposited by cold waters of meteoric 

 origin. They do not extend below the permanent water level 

 of the district. The workable deposits occur in the nearly hori- 

 zontal Fernvale limestone and Cason shale of Ordovician age 

 and in residual clays which were mainly derived from these two 

 formations. Most of the masses in the clays are residual, having 

 been freed from the above-named formations by their decompo- 

 sition; the others have been formed by the replacement of the 

 clays by manganese oxides. 



The hausmannite is present at a large percentage of the nearly 

 200 mines and prospects in the district. It occurs partly in the 

 Fernvale limestone as a replacement material but mostly in clay 

 as residual masses that have been set free by the decomposition of 

 the limestone. It has not been found in deposits that have been 

 formed by the replacement of the Cason shale and residual 

 clays. This apparently means that there was a smaller supply 

 of available oxygen for the formation of manganese oxides in the 

 limestone than in the shale and clays, because hausmannite 

 contains a smaller percentage of oxygen than the other man- 

 ganese oxides that are present in the district. 



Hausmannite, if chemically pure, would contain 72 per cent 

 of manganese which is greater than that found in the other 

 important ore-forming minerals which are psilomelane and 

 braunite ; but on account of the presence of psilomelane and other 

 impurities perhaps no sample containing the theoretical per- 

 centage can be obtained, though the percentage of manganese 

 in a sample from the W. T. Gray mine of which an analysis is 

 given on page 4 is 70.76. The presence of hausmannite in the 

 high-grade ores accounts for the fact that many carload ship- 

 ments of such ore have contained between 55 and 60 per cent of 



